About a month ago, I noticed antifreeze puddles on the driveway.
After some examination, it appeared to be a leak from the
gasket on top of the water pump. The pump itself was obviously working,
since the car was not overheating.

So, rather than opening up everything and replacing the gasket, I started smearing it with some gasket grease and kept spraying some WD-40
where I could reach.

Bottom line...After a couple of weeks, I have not seen any leaks.
Hopefully, this will last for a long while.
Sometimes, the simplest fix is the way to go!
--
-Cool Volvo- 1989 240 5 Spd w/ 303K, 1989 240 5 Spd w/ 231k. Past proud owner of 1966 122, 1968 144, 1970 145, 1972 144, 1980 245, 1982 240 4 Spd OD

I'd still be planning for a pump replacement with the gasket and seals. The problem is most likely the mushroom gasket thing on the top of the pump, which will swell when exposed to some chemicals. The swelling won't last forever, of course. You may have bought yourself some time, which is fine, but still plan for some down time to replace the pump (IMO).
--
Phoenix, AZ; 2005 S80 2.5 71k; Many past 2/7/9 models; 2015 Subaru Forester premium manual... 3k

"The problem is most likely the mushroom gasket thing on the top of the pump"
Yes, it tends to harden and compact from the heat.

"but still plan for some down time to replace the pump (IMO)"
I would just plan on replacing the gasket because that is all that needs to be replaced. Water pumps last a long time. And the quality of the one on the car may be better than its replacement.


--
1980 245 Canadian B21A with SU carb, M46 trans, 3:31 dif, in Brampton, Ont.

I would agree that only replacing the mushroom seal will be necessary (an installation "kit" can be purchased from Volvo if only the mushroom needs replacing--the kit should include the mushroom, the gasket and the "O" ring for the water pipe)-- but only if a careful inspection of the pump is performed - any sign of leakage from the "weep hole" on the bottom of the pump or from the pump shaft seal or any play at all in the shaft will call for pump replacement as well -- the rubber mushroom will have had to be there a long time before shrinkage and hardening have taken place. Personally, over the years I've had good results from a low cost pump brand--GMB. -- Dave

Problems don't fix themselves so if you like Russian roulette keep playing.

I beg to differ...There have been several cases where the bricks fixed themselves.
In this case, the gasket must've dried out and the grease/silicone softened it up to make better contact.
--
-Cool Volvo- 1989 240 5 Spd w/ 310K, 1989 240 5 Spd w/ 231k. Past proud owner of 1966 122, 1968 144, 1970 145, 1972 144, 1980 245, 1982 240 4 Spd OD

Sorry but I don't believe in magic, but good luck!
Dan